Electrical circuits



Dec. 14, 1948.

J. n. cooNEY 2,456,050

ELECTRICAL CIRCUITS Filed April 12, 1945 4 sheets-sheet 1 czbababa.

D- 14, 1948- J. R. cooNEY 2,456,050

' ELECTRICAL cIRcUI'rs Filed April 12. 1945 4 sheets-sheet 2 AAAS# lINVENTOR.

ci/511 R. 600116? BY @LA A T1' ORNEY.

Dec. 14, 1948. J. R. cooNr-:Y 2,456,050

y ELECTRICAL CIRCUITS Filed April 12, 1945 4 ShBtS-Sheet 3,/

lllllll AAAAAAA "IVY" "7'".

INVENTOR.

elo/11 R. Caorle? Y @QM ATTORLEX Dec. 14, 1948. J. R. cocNEY ELECTRICALCIRCUITS Filed April 12, 1945 4 Sheets-Sheet 4 BY Vg INVENTUR. Jah R.

Patented Dec. 14, 1948 -UNITED STATES PATENT OFFICE4 ELECTRICAL CIRCUITSJohn R. Cooney, Waldoboro, Maine Application April 12, 1945, Serial No.588,011

8 Claims. (Cl. 175-363) operation whereby such unidirectional voltage isrendered free of its usual ripple component and is made to respond veryquickly and very accurately to an increase in the amplitude of thealternating voltage and to respond with a predetermined time delay inresponse to a decrease in this amplitude.

In the achievement of this object, the alternating voltage is rectifiedand utilized to charge different capacitors. These capacitors are sointerconnected that the first of them is discharged at the beginning ofthe positive half-cycle of the altem-ating voltage and the second isdischarged at the beginning of the negative half-cycle of thealternating voltage.

During the negative half-cycle of the alternating voltage, the firstcapacitor is maintained charged to the peak value of the alternatingvoltage and the second capacitor, which is much smaller than the firstcapacitor, is maintained charged to the peak value of the immediatelypreceding positive half-cycle. At the end of the negative half-cycle ofthe alternating voltage, the first capacitor is discharged. During thenext positive half-cycle of the alternating voltage, the first capacitoris charged to the peak voltage of this half-cycle. This peak voltage isalso applied to the second capacitor which may be at a lower or highervoltage depending on the voltage of the last preceding positivehalf-cycle. At the beginning of the next negative half-cycle, the secondcapacitor is discharged and is immediately recharged from the iirstcapacitor to the peak voltage of the last positive half-cycle aspreviously explained.

In order to ensure that the first capacitor is always charged to thepeak voltage of the preceding positive half-cycle, it is made of smallcapacity and is charged through a low resistance transformer andrectifier. As already indicated, the second capacitor is madesufiiciently small to permit it to be charged to the peak voltagewithout appreciably reducing the voltage of the first capacitor. Underthe circumstances, (1) the unidirectional output voltage increases veryrapidly in response to increase in the peak value of the alternatingvoltage, (2) is maintained at the peak value of the preceding positivehalfcycle for one-half cycle after a decrease inthe peak value of thealternating voltage, and (3) decreases very rapidly at the end of thishalf-cycle.

Important objects of the invention are the provision. of means forderiving a unidirectional voltage output which is more nearlyproportional to the peak value of an alternating voltage input that hasbeen realized heretofore; and the provision of an alternating voltagepeak responsive circuit which (l) responds to an increase in such peakvoltage without appreciable time delay and (2) responds similarly to adecrease in such peak voltage after a predetermined time delay.

The invention will be better understood from the following descriptionconsidered in connection with the accompanying drawings and its scope isindicated by the appended claims.

Referring to the drawings:

Figure 1 is a wiring diagram of a simplified circuit illustrating theessential elements of the invention.

Figures 2 to 5 are explanatory curves relating to the operation of thecircuit illustrated by Fig. 1, v

Figure 6 is a wiring diagram of a preferred embodiment of the invention,

Figure 7 is a wiring diagram of another embodiment of the invention, and

Figures 8 to 16 are explanatory curves ing to the operation of thecircuit of Fig. '1.

'I'he simplified circuit of Fig. 1 includes an alternating voltage inputtransformer 20, the secondary winding of which is connected through arectifier 2| to a iirst capacitor 22 and through the rectiiier 2l and arectifier 23 to a second capacitor 24. Connected in shunt to thecapacitor 22 is a switch 25 for discharging it through a resistor 26.Likewise connected in shunt to the capacitor 24 is a switch 21 fordischarging it through a resistor 28. A filter 29-30 may be provided inthe output circuit if desired. Unidirectional voltage proportional tothe peak value of the alternating voltage input is delivered either atthe terminals 3I-32 or at the terminals 33-34.

Thus assuming the alternating input voltage wave to be a simple sinewave of constant amplitude as indicated by the left-hand part of Fig. 2or of variable amplitude as indicated by the right-hand part of Fig. 2,the capacitor 2.2 to be completely discharged by momentarily closing theswitch 25 at the points a of the wave and the capacitor 24y to becompletely discharged by momentarily closing the switch 21 at the pointsb I of the wave, the potential of the capacitor 22 varies as indicatedby the left-hand curvevof Fig. 3 in the case of a constant amplitude.signal and by the right-hand curve of Fig. 3 in the case of a variableamplitude signal. The output .potencase of a variable amplitude signal.lill-3@ is included in the circuit, thevv output Lce tial attheterminals of the capacitor 2li varies as indicated bythe left-hand curveof lig. 4. in the tential is as indicated by the full line curve oi Fig.5. Lt will be noted that the output 'curve reaches the peak value of thealternating input voltage very quickly when thisvalue increases but doesnot follow a decrease in this vaine Luitil the end of the next halfcycle. These curves are copied from oscillograms taken during operationof the modifications of Figs. 6 and l which are hereinafter explained.During such operation, the capacities of the capacitors 22 and 2t wererespectively 0.001 mid. vand. 01.0002 mid. The capacitor discharge pathin both cases was about l,000 ohms, and the sine wave input had afrequency of 40o cycles.

if the sine wave input has a constant amplia tude, as indicated by theleft-hand part of Fig. 2, it is evident that the switches 25 and 2l (andthe corresponding switches of Figs. 6 and 7) would be superuous for thereason that a simple rectier andcapacitor without any bleeder resistorwould be a satisfactory means of producing a unidirectional voltageproportional to peak value of the alternating potential applied to theinput circuit of the apparatus. The sine wave of constant amplitude,however, is considered only :for explanatory purposes. Such constantamplitude Waves are seldom, if ever, encountered for any considerableperiod of time in the case of audio frequency waves.

It is Well known that the amplitude of audio waves changes almostcontinuously. It is the function of the present invention to produce asubstantially instantaneous rise in the unidirectional output voltagewhen the peak value of the alternating input voltage rises and to delaychange in the unidirectional output voltage for one half cycle when thepeak value of the amplitude of the alternating input voltage decreases.This is illustrated by the right-hand curves of Figs. 2 to 5 It will benoted that the first cycle of Fig. 2 produces an output potential whichincreases to and is maintained at a constant value as indicated by Fig.4. The second cycle of Fig. 2 is of greater amplitude than the rst andproduces a corresponding rise in the output voltage of Fig. 4. The thirdcycle of Fig. 2 is of greater amplitude than the second and produces acorresponding rise in the output voltage of Fig. 4. The fourth cycle ofFig. 2 is of lower amplitude than the third but the output voltage ofFig. 4 decreases only after a delay of one half cycle when the switch 21is closed at the point b, as previously explained. It thus follows thatchange in the value of the unidirectional output is always delayed forone half cycle when the peak value of the alternating input potentialdecreases. It is apparent that this result is altogether dependent onthe operation of the switches 25 and 2l at the times indicated and cannot be produced by the rectifiers alone. As is well known, this resultis useful in various processes such as the photographic recording ofsound where a shutter or other instrumentality is utilized to maintainthe transparent areaof the "record at the lowest value required toaccommodate the volume of the recorded sound. I

This is so because (1) the capacitor 22 is charged through a lowresistance transformer winding and a low resistance rectifier so that itby the circuit of Fig. 6.

charged the pear: voltage of the positive if wave. 2l the capacities oithe capacitors Pl e so related that charging ci the vfrom the capacitor22 does not ap- .uce the voltage oi the capacitor Icapacitor isdischarged through and the resistor at the end oi e nali cycle, and (e)thecapacitor through the switch 2i andthe each positive half cycle.,ycie of one peak value positive li cycle or" a lower pear; ie chargeproduced on the capacitor 3ft lgher positive is maintained during halflP lower peair value. After this delay o i" cycle. however, the switchEl closes and A capacitor 2d is discharged. This condition isexemplified in Figs 2 to 5 by the two full e, preceding the lastpositive halt cycle the right ci these figures.

From a practical viewpoint, the simplined circuit of Fig. i has certainlimitatons. in the lrst place, it includes no suitable means foroperating the switches 25 and 21 at the required speed. In the secondplace, it includes no means for ensuring that the capacitors 22 'and 24are completely discharged -when the input voltage terminates suddenly.Practical operation of the circuit requires that .the switches-.operateat the frequency of the input voltage and that the capacitors becompletely discharged when the input voltage is rst applied. This isaccomplished The lower4 part of Fig. 6 corresponds to Fig. 1 but differstherefrom in that the capacitor discharge switches are in the form oftriodes 25 and 2l, a'cathode follower 49 is provided for'isolating thecapacitor 24 and its charging circuit 23-5I from the capacitor 22, and acathode follower 50 is likewise interposed between the capacitor 24 andthe output circuit. The upper part of Fig. 6 is a control circuit bymeans of which the capacitors are discharged at the proper times and aremaintained in a discharged condition, after a sudden interruption of theinput voltage, untl the input voltage is re-established.

This control circuit includes a multivibrator 35-36-31-38-39--40 whichoscillates at a relatively low frequency, determined by the values ofthe resistors 31 and 38 and the capacitors 39 and 40, when noalternating potential is applied to the input transformer 20. Whenalternating voltage is applied to the input transformer 20, thisoscillator action ceases and thecontrol circuit is operated at thefrequency of the input voltage.

In either case, there are impressed on the differentiating circuits 4 I-4'2 and 43-44 square voltage pulses such as those indicated at 45 and46. The output of these differentiating circuits is in the form of sharppeaks (indicated .at 41 and 48) which are applied to the triodes 25 and21 at the proper times for discharging the capacitors 22 and 24 aspreviously described. Bias potential is applied through a lead 6| fornormally biasing the switching tubes 25 and 21' well beyond cut-off sothat they are conductive only for a very short interval of time.

It is evident that the voltage applied to the rectifier 2| is alwayszero at the moment the capacitor 22 is discharged through the switchingtrlode attempting to disconnect the capacitor 24 while it is beingdischarged as was done in the case of Fig. 1, this capacitor is madevery small and charged through the fairly high resistance of theresistor 5|. The time constant of the charging circuit is still smallenough to bring the capacitor 24 to its full charge practicallyinstantly and the curveof Fig. 12, the curve of Fig. 13 and the curve ofFig. 14. The voltage of the capacitor 24 is indiresistor 5I prevents thecathode follower 49 from -being loaded excessively while the capacitor24 is being discharged through the triode 21 and, ,at the same time,assures a large enough ratio of the voltage drop of the resistor 5| tothe voltage across the triode 21 during the discharge period. Otherwisethe operation of the circuit of' Fig. 6 is similar to that of thecircuit of Fig. 1.

Thus assuming the secondary polarity of the transformer 20 to be suchthat a positive potential is applied to thegrid ofthe triode 35, (1) theback end of the resultant output wave 45 iunc-v tions through thediierentiator 4|42 to produce a positive pulse 41 at the grid of thetriode 25, (2) the capacitor 22 is discharged through the triode 25. and(3) the current, of the cathode follower 49 is reduced or interrupted sothat the rectiiler 23 ceases to conduct current.l

During the next half cycle, the grid of the triode 36 is positive, thecapacitor 22 is charged through the rectifier 2|. land the capacitor 24is charged through the cathode follower 49 (which has .its grid.potential applied from the capacitor 22) the resistor 5| and therectiiler 23. At the end of this half cycle (grid of 36 positive), (1)the back end of the output pulse 48 is dierentiated by the diferentiator43-44 to produce a positive pulse 48 at the grid of the triode 21, (2)the vcapacitor 24 is discharged through the triode 21,

and (3) the current of the cathode follower 50 is interrupted. Duringthe next half cycle (grid of 35 positive), the capacitor 24 is chargedthrough the cathode follower 49, the resistor 5| and the rectifier 23.At the end of this half cycle, the capacitor 22 is again discharged aspreviously explained.

The circuit of Fig. '1 is similar to that of Fig. c4

in many respects. the main dilerences being (1) in the means utilized toderive the voltage by which the switching tubes 25 and 21 are controlledand 2) in the means utilized to ensure that the capacitors 22 and '24are com-pletely discharged after a sudden cessation of the inputvoltage. Like parts oi Figs. 6 and 7 are indicated by the same referencenumerals.

In the circuit of Fig. 1, the tube 52 is a high-u twin triode which maybe precede by an amplifier (not shown), is driven to saturation by anyinput voltage above a certain minimum and delivers a substantiallyconstant-amplitude rectangular output which is differentiated, aspreviously eX- plained in connection with Fig. 6, to form the sharppulses 41 and 48 by which the capacitors 22 and 24 are dischargedthrough the triodes 25 and 21.

The Wave forms of the voltages applied to the control grid of the uppertriode of the tube 52, to the differentiator 4I-42, and to the controlgrid of the triode 25 are indicated, respectively, by the curve of Fig.8, the curve of Fig. 9 and the curve of Fig. 10. The voltage of thecapacitor 22 is indicated by the curve of Fig. 11.

The wave forms of the voltages applied to the control grid of the lowertriode of the tube 52, to the diiferentiator 43-44, and to the controlgrid of the triode 21 are indicated respectively by the cated by thecurve of Fig. 15 and that of the output circuit by the4 curve of Fig.16.

While the negative pulses of the curves I0 and |4 should theoreticallyhave no eiTect on the triodes and l21 because they are already cut offwhen these negative pulses occur, it is advantageous to absorb them bymeans of the diodes 53 and 54.

For ensuring that the capacitors are completely discharged after a'sudden interruption of the input voltage of the transformer 20, there isprovided a twin diode 55 which is normally biased to cutoffv by thevoltage drop of; a resistor 56 so that the triodes 25 and 21 arenormally biased on by a voltage applied to the lead 51. The applicationof a certain minimum input voltage to the transformer 20 and to atransformer 58, however,

Vproduces in a resistor 59 a voltage drop whereby the tubes 25 and 21are restored to their normal cut-off condition. The anodes of the tube55conduct alternatelyA except for a very short time at cross-over. Thepositive pulse which tends to appear every half-cycle for this reason isironed out by a small capacitor 60 It is thus ari-parent (l)thatthevmultivibrator oscillator of Fig. 6 is replaced' in Fig. 7 by thesaturation limiter 52 and by the twin triode 55 through which grid biaspotentials of the tubes 25 and 21 are controlled. (2) that the tubes 25and 21 are biased on periodically at a low irequency in the absence ofinput voltage to the circuit of Fig. 6. and (3) that the tubes 25 and 21are continuallj,7 biased on in the absence of input voltage to thecircuit of Fig. 7. In either case the capacitors 22 and 24 are alwaysfully discharged when voltage is applied to the input transformer 20 andthe unidirectional output Voltage increases as previously explained.

The operatori of the modication of Fig. 7 is similar to that outlined inconnection with Fig. 6.

What the invention provides is a system for converting an alternatingpotential to a unidirectional potential which responds immediately to anincrease in the alternating potential amplitude but responds with apredetermined time delay to a decrease in the alternating potentialamplitude.

I claim as my invention:

1. The combination of means for applying an alternating voltage, a firstcapacitor, a second capacitor having a capacitance which is small ascompared to that of said rst capacitor, means for rectifying saidvoltage and for appl-ying said rectified voltage to said capacitors.means for discharging said rst capacitor at the beginning of eachpositive half-cycle of said voltage, and means for discharging saidsecond capacitor at the beginning of each negative half-cycle of saidvoltage whereby the unidirectional voltage output of said device isincreased rapidly in response to an increase in the amplitude of saidalternating voltages and decreases at a predetermined time after adecrease in the amplitude of said alternating voltage.

2 The combination of means for applying an alternating inout voltage, afirst capacitor, a second capacitor having a capacitance which is smallwith respect to that of said-first capacitor, means for rectifying saidalternating voltage and for applying said rectified voltage to saidcapacitors, and means responsive to said alternating voltage fordischarging said rst capacitor at the begin- 7 ning of each positivehalf -cycle and for discharging said second capacitor at the beginningof each negative half-cycle of said alternating voltage.

3. The combination of means for applying an alternating input voltage, afirst capacitor, a second capacitor, means for rectifying saidalternating voltage and for applying said rectified voltage to saidcapacitors, and means including a multivibrator responsive to saidalternating volt.

oscillation generator for discharging said capacitors in the absence ofsaid alternating voltage.

4. The combination of means for applying an alternating input voltage, aiirst capacitor, a second` capacitor, means for rectifying saidalternating voltage and for applying said rectiiied voltage to saidcapacitors, and means including diilerentiating circuits and a pair oftriodes controlled by said alternating voltage for discharging saidcapacitors successively in response to successive half -cycles of saidalternating voltage.-

5. The combination of means for applying an alternating input voltage, arst capacitor, a second capacitor, means for rectifying said alternatingvoltage and for applying said rectified voltage to said capacitors, andmeans including a saturation limiter responsive to said alternatingvoltage for discharging said capacitors successively in response tosuccessive half-cycles of said alterhating voltage.

6. The combination of means for applying an spouse to successive cyclesof said alternating voltage, and mean for maintaining said electrondis-- charge devices in a conductive condition in the absence of saidalternating voltage. 7. The combination of means for applying analternating input voltage, a first capacitor, a second capacitor, meansfor rectifying said voltage and for applying said'rectied voltage tosaid capacitors, means for discharging said tlrst capacitor at thebeginning of each positive halfcyclevof said voltage, means fordischarging said second capacitor at the beginning of each negativehalf-cycle of said voltage, and means for isolating the charging circuitof said second capacitor fromlsaid first capacitor. l

8. The combination of means for applying an alternating input voltage, ailrst capacitor, a second capacitor, means for rectifying said voltageand for applying said rectied voltage to said capacitors, means fordischarging said iirst capacitor at the beginning of each positivehalfcycle of said voltage, means for discharging said second capacitorat the beginning of each negative half-cycle of said voltage, and meansinclud- 25 ing a cathode follower for isolating the charging circuit of.said second capacitor from said iirst capacitor.

JOHN R. COONEY REFERENCES CITED The following references are of recordin th file of this patent:

UNITED STATES PATENTS Number Name Date 1,896,468 Shoemaker Feb. 7, 19332,075,120 Lenehan Mar. 30, 1937 2,239,786 Jones Apr. 29, i941 402,343,285 Dodington Mar. 7, 1944

